1. Technical Field
The present invention pertains to temperature sensing devices, such as the types of temperature sensing devices disclosed in: U.S. patent application Ser. No. 10/849,251, entitled “Temperature Sensing Device for Selectively Measuring Temperature at Desired Locations Along an Intravenous Fluid Line” and filed May 20, 2004, now U.S. Patent Application Publication No. 2004/0249336 (Faries, Jr. et al.); U.S. Pat. No. 7,090,658 (Faries, Jr. et al.); and U.S. Pat. No. 6,824,528 (Faries, Jr. et al.). The disclosures of the foregoing patents and patent application publication are incorporated herein by reference in their entireties. In particular, the present invention pertains to devices that monitor temperature of an intravenous fluid at any desirable location along a fluid line (e.g., an intravenous (IV) fluid line) and may further selectively enable and/or disable the flow of fluid through those devices to ensure a desired fluid temperature is attained within the fluid line prior to entering a patient.
2. Discussion of Related Art
A patient is typically infused with intravenous (IV) fluids utilizing a liquid filled bag or container and an IV fluid line that delivers fluids under gravity and/or applied pressure from the container to the patient. It is important in many situations to maintain the temperature of the fluid in the IV line within a desirable and safe temperature range upon entering the patient so as to eliminate any potential for thermal shock and injury to the patient by the fluid.
Accordingly, the related art provides several devices that employ temperature sensors to monitor and/or control the temperature of fluid flowing within an intravenous or other type of fluid line. For example, U.S. Pat. No. 5,729,653 (Magliochetti et al.) discloses a device for heating a fluid to a body temperature prior to delivery of the fluid to a patient. In one embodiment, a fluid to be warmed prior to delivery to a patient can be passed through a flow through chamber disposed in the fluid delivery line. An electrically resistive heating element for heating the fluid can be molded into the chamber to heat the fluid from room or ambient storage temperatures to a body temperature of the patient. A probe of a temperature monitoring element can be used to monitor the temperature of the fluid exiting the chamber. In another embodiment, this information can be relayed back to a controller for controlling the power to the resistance element, and hence, the temperature of the fluid. In still another embodiment, an infrared temperature sensor can be used for monitoring the temperature of the fluid exiting the chamber by scanning through a window in the chamber outlet port or elsewhere in the fluid line. The device may further include an LED two-digit display of the exiting fluid temperature for visual temperature monitoring.
U.S. Pat. No. 5,250,032 (Carter, Jr. et al.) discloses a heater for warming blood, plasma and other solutions flowing through an IV tube prior to entry into a patient. The heater is releasably secured to a patient and includes a housing having an elongated channel extending from one end of the housing to its other end. The channel is formed with an elongated slot against which a heating element is mounted. The heating element is controlled by a control circuit and powered by batteries. The control circuit may energize the heating element continuously or cyclically in response to sensed temperatures.
U.S. Pat. No. 3,526,134 (Schaus) discloses a thermobulb mount for holding a temperature sensing element in a pipeline so as to prevent damage to the element which might otherwise be caused by fluid flow within the pipeline. The mount includes a body having threaded ends for connection in series with a pipeline, an installation boss with a hole through which the sensing element extends and a recess formed on the inside of the pipeline opposite the boss for supporting an outboard end of the sensing element.
U.S. Pat. No. 5,829,880 (Diedrich) discloses a device including a T-type pipe combination including a medium conduction pipe and a connection piece projecting away from the pipe. The pipe is connected to tubing that supplies medium to and leads medium away from the pipe. A plug unit is disposed within the connection piece and includes a stopper supporting contact pins, as well as a temperature sensor connected to those pins. The temperature sensor indirectly measures the temperature of the medium flowing through the pipe. An electrical bush part is further secured to the connection piece via a bracket and is connected to the contact pins. The bush part housing includes contact bushes with electrical connecting lines that extend externally of the housing through openings defined therein.
U.S. Pat. No. 4,138,890 (Brown) discloses a temperature indicating probe including a liquid-in-glass thermometer encased within a housing. The housing includes a series of tapered, cylindrical shaped portions separated by a step or shoulder, which are respectively insertable into variously sized standard medical appliance line openings or fittings, for sensing and indicating the temperature of the working fluids being carried through the line.
U.S. Pat. No. 4,476,877 (Barker) discloses a temperature sensing device for use in a fluid flow system. The device includes a housing with a tapered lumen extending through the housing, an opening extending through the housing and a thermally conductive enclosure inserted within the opening. The thermally conductive enclosure extends substantially fully across the lumen. A thermistor temperature sensor is potted in a carrier to be received within the enclosure in order to determine the temperature of injectate flowing from a syringe through the lumen. The measured temperature is utilized to determine desired blood flow rate information.
U.S. Pat. Nos. 6,248,077 and 6,336,902 (Elson et al.) disclose a system for sensing a characteristic of fluid flowing to or from a human body comprising a conduit having a first end adapted to be outside the body, a second end adapted to be received within the body, a flow passage through which fluid can flow between the first and second ends and a probe including a sensor for sensing a characteristic of the fluid. The probe is mounted on the conduit with the sensor in the flow passage. The sensor is isolated from the fluid flowing in the flow passage.
The related art suffers from several disadvantages. In particular, the Magliochetti et al. and Carter, Jr. et al. systems have size and/or mounting requirements that tend to restrict system application to particular sections of an IV line. Thus, operators are required to estimate, or adjust system settings to compensate for, conditions at desired IV line sites outside the system application range. This may lead to inaccuracies in fluid temperature control and measurement for the desired sites, thereby risking injury to a patient. In addition, the Carter, Jr. et al. system measures temperature for temperature control of fluid without providing any temperature indication to an operator, thereby enabling infusion of fluid of unknown temperature into a patient.
The Schaus and Diedrich devices are designed for non-medical fluid systems. Accordingly, these devices are employed for non-sterile applications and are ill-suited for medical applications that require sterility. Although these devices measure fluid temperature, the devices generally do not provide a displayed temperature to an operator. Thus, fluids may attain inappropriate temperatures without notice to the operator which may lead to undesirable conditions or consequences. The Brown device requires an operator to manually observe a thermometer and determine a fluid temperature therefrom. This is distracting to the operator and permits possible operator error to be introduced with respect to the fluid temperature measurement, thereby enabling infusion of fluid at an inappropriate temperature and risking injury to the patient.
The Elson et al. (U.S. Pat. Nos. 6,248,077 and 6,336,902) and Barker systems do not provide temperature control of the fluid, or a manner within the line to control the fluid flow. This may enable infusion of a fluid at an inappropriate temperature into a patient, thereby increasing the risk of injury.